Comparisons were made between 236 Wilms' tumor patients with metastasis to the lungs and/or liver at initial diagnosis who were registered on the National Wilms' Tumor Study (NWTS) during 1969 to 1983, and 1755 patients who did not have overt metastases at diagnosis. Patients with evidence of regional spread of disease beyond the kidney, especially if to the renal vein or lymph nodes, were much more likely to have overt metastases present at diagnosis than those with apparently localized disease. The presence of metastases was also correlated with age at diagnosis, ranging from 1% among infants younger than 1 year of age to 24% for those aged 6 years or older. The percentage of tumor deaths for patients with metastases at diagnosis (Stage IV) and a primary tumor of favorable histology (FH) declined from 29% at 2 years postdiagnosis on the first therapeutic trial (NWTS-1) to 9% for the most recent one (NWTS-3), and is now comparable to that for patients without metastases but with nonresectable local invasion at diagnosis (Stage III). The local extent of disease also influenced the survival outcome for Stage IV/FH patients. Survival was poor for those with anaplastic or sarcomatous (unfavorable) histology, regardless of local staging or trial. There was no difference in survival according to metastatic site (liver +/- lung vs. lung only) if present prior to treatment. By contrast, patients who developed liver metastases during or after treatment had an especially poor chance for survival as compared with those who developed lung deposits at those times.